An example of the constitution of a prior art device for identifying gas appliances is given below.
Gas meters equipped with a gas flow meter at the opening of a gas supply line are typically installed in residential buildings.
Conventional gas meters achieve different billing schemes for respective appliances by obtaining a volumetric sum when gas flows during a specified time zone and a volumetric sum when gas flows within a specified flow volume range. That is, the flow volume for each time zone and the flow volume for each flow volume zone are determined, so as to establish a billing scheme using these volumetric sums. An example of such a prior art billing scheme is described with reference to FIG. 10. A predetermined discount flow rate zone and a predetermined discount time zone are set in advance, and a discount is applied to gas fees for flow volumes corresponding to this discount flow rate zone and this discount time zone. Thus, the shaded areas shown in FIG. 10 correspond to the zones subject to this discount (see, for example, Japanese Patent Application Kokai Publication No. 2002-71421).
However, this method falls short in identifying specific appliances, and thus does not readily provide a billing statement that is easy to understand and convenient for customers to identify charges billed for specific appliances.
Accordingly, the present Applicant has disclosed a method for identifying specific appliances, as described below (see, for example, Japanese Patent Application Kokai Publication No. 2006-313114).
The operation of the disclosed example is now described. Gas flow volume is measured with a gas meter at 2-second intervals, and this data is delivered to a differentiator to differentiate the flow volume value, which is then output as differentiated flow volume data for every 2 seconds.
This differentiated data is sequentially delivered to a profile finder and is then compared against comparative values stored in a memory. If the differentiated values exceed the comparative values, then a change is deemed to have occurred in the state of a gas appliance. Once a change is detected, then the identification means makes a comparison with the comparative profiles for each gas appliances stored in the memory, so as to identify the appliance and the state thereof.
Since activation identification of an appliance is performed by differentiating the flow volume values, it is relatively easy to perform activation identification of an appliance, even if another appliance is activated in a state in which another appliance is already operating.
In the above-described prior art configuration, if there is a failure in identifying an appliance for any reason, even if the appliance consumes some volume of gas, the gas consumption of the appliance cannot be recognized as a gas consumption and is treated as an error. Further, once a failure in identification occurs, it is difficult to correct, resulting in that there remains a lack of transparency in reliability in appliance identification.
The present invention eliminates the above-described drawback, and provides a gas appliance identification device with improved accuracy in identifying appliances, reducing errors in measuring appliance flow volume by performing identification again by a different means, if there was an error in identifying an appliance.